Apparatus for spinning hollow bicomponent filaments

ABSTRACT

An apparatus for spinning hollow bicomponent filaments. The apparatus includes a distributor, a spinneret having holes and a shim having openings fixed between the distributor plate and the spinneret. The distributor supplies a first polymer having an MV to a first part of the spinneret holes and a second polymer having a lower MV to a recessed section of the spinneret. The shim openings are positioned above the spinneret holes and extend away from the first part of the holes to allow the second polymer to flow from the recessed section, through the shim openings, to a second part of the spinneret holes. The two polymers travel along the opposed first and second parts of the holes until exiting the spinneret through respective asymmetric C-shaped apertures. The apertures are sized so that hydraulic split does not occur between the polymers and consequently potential filament kneeing is obviated. Upon exiting the apertures, the polymers self-join to form hollow filaments and are quenched. Since the polymers have different MV properties, the filaments self-crimp into a spiral configuration.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to a method and apparatus for spinninghollow bicomponent filaments. More particularly, the invention relatesto using a spinneret and a shim for hollow bicomponent filamentspinning. More particularly still, the spinneret has a plurality ofcapillaries having asymmetric apertures, and the shim has a plurality offan shaped openings.

2) Prior Art

Mono-component filaments are well-known and a variety of spinning packsand spinnerets have been employed in the production of hollow filaments.A conventional mono-filament spinning assembly involves feeding polymerthrough spinneret holes then forcing the polymer through apertures atthe bottom of the hole to form a hollow filament. Subsequently, thefilament can be mechanically crimped to provide additional bulk.

Spinning packs are also well-known for the production of bicomponentfilaments having side/side and sheath/core configurations. Aconventional bicomponent spin pack assembly involves feeding moltensheath forming material to spinneret holes, in a direction perpendicularto the holes, and injecting molten core forming material into the sheathforming material as it flows into the spinneret holes.

Traditionally, use of bicomponent polymers to produce hollow filamentshas been impeded by kneeing of the filament. For bicomponent hollowfilament production, the polymers must first be fed to opposed parts ofthe spinneret hole and through opposed apertures in a bottom of thespinneret hole. Since the polymers have different melt viscosities(hereinafter MV) there is more resistance to the higher MV in goingthrough its designated aperture than for the lower MV in going throughits designated aperture. The difference in MV causes a hydraulic splitwhere the higher MV polymer partially splits to egress the aperturedesignated for the lower MV polymer. The lower MV polymer, forced toegress a reduced aperture area, exits at a higher velocity causing thefilament to “knee”, that is veer substantially from a linear direction.Kneeing causes operational problems with the spin pack such asdifficulty in extruding the filaments and increased filament breakage.

Accordingly, there is a need for an improved spin pack assembly whereina hollow bicomponent filament can be produced without excessive kneeing.Additionally, there is a need for an improved shim for directing onepolymer to a designated part of the spinneret hole. Further there is aneed for improved spinneret openings each having apertures configured inthe capillary to eliminate hydraulic split of the polymers. Lastly,there is a need for a self-crimping hollow bicomponent filament.

SUMMARY OF THE INVENTION

The present invention is directed towards a spin pack assembly andmethod for spinning hollow bicomponent filaments which do not knee andare self-crimping. Since each polymer has different properties, and inparticular substantially different shrinkage rates, the bicomponentfilaments will self-crimp in spiral after being drawn and heated. Thespiral crimp bicomponent filaments have substantial bulk suitable foruse in fiberfill for sleeping bags, winter quilted clothing and othersimilar applications requiring a high thermal insulation “R” value.

The spin pack assembly forms hollow self-crimping filaments by utilizinga unique shim and a spinneret having openings with asymmetric aperturesto separately handle at least two polymer streams. Upon exiting theapertures, the polymer streams join to form self-crimping hollowfilaments. The shim is provided with a plurality of openings whichdirect a first polymer to a first part of the spinneret holes whilerestricting the first polymer from a remaining part of the holes.Distributor holes offset from the holes in the spinneret, deliver asecond polymer to the opposed remaining part of the spinneret holes. Thepolymers are then forced through separate apertures provided in a lowersection of the spinneret holes. The apertures are configured to avoidhydraulic split of the polymers and accordingly avoid kneeing of theresulting hollow bicomponent filament.

In the broadest sense, the present invention also is directed towards aspin pack assembly comprising a distributor having outer flow passagesfor the flow of a first polymer and an inner polymer flow passage forthe flow of a second polymer, and a spinneret secured relative to thedistributor and communicating with the distributor to receive the firstand second polymers. The spinneret has a top face directed towards thedistributor, an opposed bottom face and a plurality of holes extendingfrom the top face to the bottom face. The holes have a lower sectionwhich is provided with a plurality of apertures. Each of the aperturescommunicate with substantially only the inner flow passage or at leastone of the outer flow passages.

In the broadest sense, the present invention also is directed towards aspin pack assembly comprising a distributor having outer flow passagesfor the flow of a first polymer and an inner polymer flow passage forthe flow of a second polymer, and a spinneret secured relative to thedistributor and communicating with the distributor to receive the firstand second polymers. The spinneret has a top face directed towards thedistributor, an opposed bottom face and a plurality of holes extendingfrom the top face to the bottom face. The holes have a lower sectionwhich is provided with a plurality of apertures in which substantiallyonly one of the first or second polymers egresses any one of theapertures. The first and second polymers flowing through the aperturesare capable of forming hollow filaments due to the configuration of theapertures.

An object of the present invention is to configure the spinneretapertures with different cross-sectional areas.

Another object of the present invention is to limit the apertures to twoC-shaped apertures.

Still another object of the present invention is to provide a shimsecured between the distributor and the spinneret. The shim is providedwith a plurality of openings having a first portion and a secondportion. The first portion is positioned between a bottom section of thedistributor outer flow passages and the spinneret holes to form acontinuous path therebetween. The second portion extends from the firstportion in a direction away from a first part of the holes to form acontinuous course for polymers to flow from the spinneret, through thesecond portion, to a remaining part of the holes which is opposed to thefirst part.

A further object of the invention is to configure the first portion incircular shape and the second portion in block-arc shape. Additionally,the first portion is coaxial with the holes, and the second portionspans an arc of about 120 degrees.

A still further object of the present invention is to provide thedistributor outer flow passages with a bottom section which is offsetfrom the spinneret holes such that if the bottom sections were extended,the bottom sections would be positioned within the first part of therespective spinneret hole.

In the broadest sense, the present invention is directed towards amethod for producing hollow bicomponent filaments. The method includesproviding a distributor having a plurality of outer polymer flowpassages which have a bottom section, and an inner flow passage. Aspinneret, secured relative to the distributor and having a top facedirected towards the distributor and an opposed bottom face, is alsoprovided. Holes are provided in the spinneret which extend from the topface to the bottom face. The holes have a first part, a remaining part,and a lower section having a plurality of apertures. The holes areaxially offset from the bottom sections such that the bottom sectionswould be positioned within the first parts if extended. A source for afirst polymer and a source for a second polymer are provided. The firstpolymer is forced through the outer flow passages, through the firstpart of the holes and through any of the apertures positioned on thefirst part of the spinneret holes. The second polymer is forced throughthe inner flow passages, through the remaining part of the holes andthrough any of the apertures positioned in the remaining part of thespinneret holes. Upon exiting the apertures, the polymers form intofilaments which are quenched.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is a fragmented perspective view of a spin pack assemblyaccording to the preferred embodiment of the invention;

FIG. 2 is a fragmented elevational view, in cross section, of the spinpack assembly of FIG. 1;

FIG. 3 is an enlarged fragmented elevational view, in cross section, ofan outer distributor passage and a spinneret hole taken through section3—3 of FIG. 2, and having an enlarged hollow filament, shown in crosssection, extending from the spinneret hole;

FIG. 4 is a plan view of a shim having openings;

FIG. 5 is an enlarged fragmented plan view of a shim intermediateopening positioned over a spinneret hole having apertures, taken throughdetail 5—5 of FIG. 1;

FIG. 6 is another embodiment of the spinneret hole shown in FIG. 5,having apertures of an alternative configuration, and with the shimremoved; and

FIG. 7 is a further embodiment of a spinneret hole shown in FIG. 5having apertures of a further alternative configuration and with theshim removed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a spin pack assembly 10 according to thepresent invention. The spin pack assembly 10 is configured in a stackand includes from top to bottom: a supply manifold 11, a distributor 12fixed beneath the manifold 11, a shim 14 fixed beneath the distributor12, and a spinneret 16 fixed beneath the shim 14. The distributor 12,shim 14 and spinneret 16 are provided with co-axial openings or threadedopenings for receiving inner and outer rings of threaded bolts 20, 22.The rings of bolts 20, 22 secure the distributor 12, shim 14 andspinneret 16 together to overcome bowing and separation of thecomponents. Additionally, the distributor 12, shim 14 and spinneret 16are relatively positioned by a central dowel 24 in the center of thespin pack assembly and by outer dowel 26 interposed along the outer ringof bolts 22. The spin pack assembly 10 components are manufactured froma high strength material such as, for example, stainless steel.

First and second polymers are forced through the spin pack assembly 10generally in the top to bottom fashion that the components are arranged.The polymers can be any spinnable polymer such as, for example,polyolefin, polyester or nylon.

The manifold 11 forces a first molten polymer and a second moltenpolymer via conventional pump and filter means (not herein illustrated)through respective outer and inner feed conduits 28, 30 to thedistributor 12. The distributor 12 is provided with radial outwarddirected feed channels 32 in the top surface of the distributor 12, anannular channel 34 formed in the bottom surface of the distributor 12,and inner passages 36 which connect the feed channels 32 to the annularchannel 34. The annular channel 34 disburses the second polymer to theshim 14 in a circular ring pattern. The shim 14 is provided with inneropenings 38, arranged in a circular ring pattern which coincides withthe annular channel 34, to allow passage of the second polymer from theannular channel 34 to a recessed section 40 of the spinneret 16.

As shown in FIGS. 2 and 3, the distributor 12 also includes outerpassages 42 which provide passage for the first polymer from themanifold 11, through the distributor 12, to the shim 14 and thespinneret 16 positioned therebeneath. The outer passages 42 have anupper counterbore 50 and a lower tapered bottom 52. The tapered bottoms52 are positioned immediately above intermediate openings 54 provided inthe shim 14.

Particularly illustrated in FIG. 3, the tapered bottoms 52 are alsospaced above, and axially offset from, corresponding spinneret holes 56.The tapered bottoms 52, intermediate openings 54, and spinneret holes 56are related such that that if the tapered bottoms 52 were extended theywould pass through the intermediate openings 54 and into a first part 60of the spinneret holes 56. That is, a passage (indicated by arrow W)guides the first polymer from the tapered bottoms 52 to the first part60 of the spinneret holes 56. Accordingly, the first polymer does notflow co-axial with a longitudinal center-line of the holes 56.Preferably, the first part 60 is the part of the holes 56 radiallyclosest to the center of the spinneret 16 (arrow X points towards thecenter of the spinneret) to maximize the property difference in thefirst and second polymers during quenching, as discussed below.

As illustrated in FIGS. 1 and 2, the spinneret 16 includes a central hub62, an outer rim 64 and the interposed recessed section 40. Cylindricalbosses 66, each provided with the co-axial spinneret hole 56, verticallyextend from the recessed section 40 and terminate in a plane common witha top surface of the outer rim 64 and the central hub 62. The recessedsection 40 defines a volume between the central hub 62 and the rim 64for conveyance of the second polymer which is received by the spinneret16 from the inner passages 36. The recessed section 40 is preferablydeeper nearer the central hub 62 and shallower near the outer rim 64 tomaintain the second polymer under constant pressure. The second polymerflows within the recessed section 40 between the bosses 66 and isconfined between the central hub 62 and outer rim 64.

The shim 14 is unitary, has a uniform thickness, and slightly separatesthe distributor 12 from the spinneret 16. Various openings in the shim14 are shown in FIG. 4 and include respective openings 67, 68, 69, 70,for receiving the inner and outer ring of bolts 20, 22 and the centraland outer dowels 24, 26. The shim 14 is also provided with the inneropenings 38 and the intermediate openings 54 to direct passage ofpolymers. The shim 14 sets in the plane common with the terminal ends ofthe bosses 66 and is flush against the bosses 66 to restrict polymerfrom entering the spinneret holes 56 except via the intermediateopenings 54, as shown in FIGS. 2, 3 and 5.

As illustrated in FIG. 3, the intermediate openings 54 are configured toallow unrestricted passage (arrow W) of the first polymer directly fromthe distributor 12 to the first part 60 of the spinneret holes 56.Additionally, the intermediate openings 54 allow passage of the secondpolymer along a continuous course (indicated by arrow Y) to a remainingpart 71 of the spinneret holes 56 opposed to the first part 60.

Although different intermediate opening 54 configurations can be used,the preferred formation, shown in FIGS. 4 and 5, consist of a circularsection 72 contiguous with a block-arc section 74. FIG. 5 illustratesthat the circular sections 72 are co-axial with, and substantially thesame size as, the spinneret holes 56. The block-arc sections 74 extendfrom the circular section 72 in a direction away from the first part 60of the spinneret holes 56 and terminate beyond the corresponding boss66. As shown in FIG. 3, the continuous course (arrow Y) for the secondpolymer is provided from the recessed section 40, through the block-arcsection 74, over the boss 66, and thereafter past circular section 72 tothe remaining part 71 of the hole 56. To obviate the second polymer frombeing trapped in dead-space near the rim 64 of the spinneret 16, theblock-arc section 74, and consequently the continuous course (Y), ispreferably oriented at a part of the hole 56 radially furthest from thecenter of the spinneret 16.

Per FIG. 5, the block-arc section 74 spans in an arc 80 in the range ofabout 90 degrees to about 180 degrees, and preferably approximately 120degrees. As a further alternative, the block-arc section 74 can bepartitioned, such as for example, by having a first block-arc sectionand a second block-arc section each spanning about 60 degrees with aland therebetween (not shown).

As shown in FIG. 3, the spinneret holes 56 are co-axial with the bosses66 and extend from a top face 82 to a bottom face 84 through thespinneret 16. The holes 56 have a counterbore top section 86, a taperedtransition section 88 and a lower section 90. The lower section 90includes opposed first and second apertures 92, 94 (more clearly shownin FIG. 5) extending from an intermediate surface 96 of the hole 56 tothe bottom face 84 of the spinneret 16.

In an embodiment, FIG. 5 shows the first aperture 92 positioned in thefirst part 60 of the hole 56 and the second aperture 94 positioned inthe opposed remaining part 71 of the hole 56. The apertures 92, 94 areshaped as ½ of a circular annulus. That is, each aperture 92, 94 extends180 degrees in an elongate arc. A pair of opposed lands 97 space theapertures 92, 94 apart and integrally join a center core 98 with thespinneret 16. The apertures 92, 94, taken with the lands 97, form aslightly elongated circular annulus. Stated another way, if theapertures 92, 94 were positioned end-to-end, they would form a circularannulus. The lands 97 are as narrow as possible so that the first andsecond polymers will join together after exiting the respectiveapertures 92, 94 while balancing the need to maintain the integrity ofthe center core 98.

Although configuring each aperture as ½ of a circular annulus ispreferred, other configurations are also acceptable such as accurate,semi-circular, oval and even linear. Apertures which are generallysemi-circular are defined as being C-shaped.

The apertures 92, 94 are further characterized as being asymmetric, thatis, each having a different cross-sectional area. The first aperture 92has a greater cross-sectional area than the second aperture 94, and inparticular, the first aperture 92 is wider than the second aperture 94.The cross-sectional areas are derived according to the MV ratio of thepolymers so that hydraulic split is avoided. Accordingly, substantiallyonly one polymer egresses from any one aperture. That is, each aperturecommunicates with substantially only the inner passages 36 or one of theouter passages 42 so that any hydraulic split is sufficiently de minimisand virtually no kneeing of the resulting filament occurs. For examplewhen using PET, the asymmetric apertures 92, 94 can be configured toenable spinning of polymer at intrinsic viscosity (hereinafter “IV”)combinations such as 0.5/0.67 IV, 0.63/0.8 IV and 0.55/0.8 IV withouthydraulic split. Each aperture configuration is prefixed on providing alarger aggregate cross-sectional area for the higher IV polymer than thelower IV polymer, based upon the IV ratio of the polymers, to avoidhydraulic split.

Alternative aperture configurations are illustrated by FIGS. 6 and 7.The alternative embodiments have the same spinneret 16, boss 66 and hole56 arrangement as discussed above, but with a different apertureconfiguration. Also, by increasing the number of lands, the center coreis further maintained against failure of lands due to stress fromhydraulic pressures of the polymers.

In particular, FIG. 6 shows an alternative aperture configurationincluding first and second apertures 100, 102 which have a largercross-sectional area in aggregate than a third aperture 104. Theapertures 100, 102, 104 are separated by respective lands 106, 108, 110and define a center core 111 therebetween. The first polymer is directedthrough the first and second apertures 100, 102 and the second polymerthrough the third aperture 104.

Similarly, FIG. 7 shows four apertures 120, 122, 124, 126, separated bylands 128, 130, 132, 134, and defining a center core 135. The first andsecond apertures 120, 122, in aggregate, have a larger cross-sectionalarea than the combined third and fourth apertures 124, 126. The higherMV first polymer is directed through the first and second apertures 120,122, while the lower MV second polymer is directed through the third andfourth apertures 124, 126.

As a further alternative, the apertures could be configured as three ormore semicircular apertures equally spaced in a circular pattern.Additionally, each aperture could be of equal cross-section or havedifferent cross-sectional areas. Likewise, linear apertures could bepositioned in the shape of a triangle with the apertures having equal ordifferent cross-sectional areas. In each case, the total cross-sectionalarea through which each polymer flows is based on the MV ratio of thepolymers to avoid hydraulic split. Accordingly, where the apertures havethe same cross-section, a greater number of apertures will be designatedfor handling the higher MV polymer than for the lower MV polymer. Themyriad of possible aperture configurations is not limited by theembodiments illustrated or described herein.

In operation, the distributor 12 receives the first and second polymersfrom the manifold 11 through the respective outer and inner feedconduits 28, 30 and directs the polymers through the shim 14 to thespinneret 16, as shown in FIGS. 1 and 2. The first polymer is pumpedthrough the outer passages 42, through the intermediate shim openings54, and thereafter is received by the first part of the spinneret holes56, as indicated by arrow (W) of FIG. 3. Per FIGS. 1 and 2, the secondpolymer is pumped to the feed channels 32, outwardly within the feedchannels 32 to the inner passages 36, and thereafter through the innershim openings 38 to the recessed section 40 of the spinneret 16. Thepressure drop between the top surface of the bosses 66 and the bottomsurface of the distributor 12, and the pressure drop between the slopingrecessed section 40 and the bottom surface of the shim 14 create anoverall pressure drop forcing the second polymer through the recessedsection 40, through the block-arc shim sections 74, and over the bosses66 to the remaining part 71 of the holes 56, as illustrated by arrow (Y)of FIG. 3.

In regards to FIGS. 3 and 5, the first polymer flows through the firstpart 60 of the holes 56 and the second polymer flows through theremaining part 71 of the holes 56. The higher MV first polymer is fedthrough the larger first apertures 92 positioned on the first part 60 ofthe holes 56, while the lower MV second polymer is fed through thesmaller second apertures 94 positioned on the remaining part 71 of theholes 56, to avoid hydraulic split. Since the lands 97 minimally spacethe apertures 92, 94 apart, the terminal sides 140 of the moltenpolymers join after exiting the apertures 92, 94 to form a hollowfilament 142 (shown in cross-section in FIG. 3). Upon exiting theapertures 92, 94, the hollow filament 142 is quenched. The quenching canbe by any suitable manner, with radial quenching emanating from thecenter of the spinneret 16 preferred. Preferably also, the larger firstapertures 92 are positioned radially closer to the center of thespinneret 16 than the corresponding smaller second apertures 94.Consequently, with radial quenching, the polymer having a higher MV isquenched at a slightly greater rate than the lower MV polymer so thatthe property differences between the polymers are maximized.

Although a composition of 50% for each polymer is ideal, the lower MVpolymer generally constitutes about 30% to 50% of the filament with atypical amount of about 40%.

Although particular embodiments of the invention have been described indetail, it will be understood that the invention is not limitedcorrespondingly in scope, but include all changes and modificationscoming within the spirit and terms of the claims appended hereto.

What is claimed is:
 1. A spin pack assembly for the production of hollowbicomponent filaments comprising: a distributor having a plurality ofouter polymer flow passages for the flow of a first polymer and an innerpolymer flow passage for the flow of a second polymer; a spinneretsecured relative to said distributor and communicating with saiddistributor to receive the first and second polymers, wherein saidspinneret includes a top face directed towards said distributor, anopposed bottom face and a plurality of holes extending from said topface to said bottom face, wherein said holes have a lower section whichincludes a plurality of apertures and wherein each of said aperturescommunicate substantially only with either said inner flow passage or atleast one of said outer flow passages; and a shim secured between saiddistributor and said spinneret, said shim having a plurality ofopenings, each of said openings having adjacent first and secondportions, wherein said first portion forms a continuous path from saidouter flow passage, through said openings to said holes, and said secondportion forms a continuous path from said inner flow passage, throughsaid openings to said holes.
 2. A spin pack assembly for the productionof hollow bicomponent filaments comprising: a distributor having aplurality of outer polymer flow passages for the flow of a first polymerand an inner polymer flow passage for the flow of a second polymer; aspinneret secured relative to said distributor and communicating withsaid distributor to receive the first and second polymers, wherein saidspinneret includes a top face directed towards said distributor, anopposed bottom face, and a plurality of holes extending from said topface to said bottom face, wherein said holes have a lower section whichincludes a plurality of apertures whereby the first polymer and thesecond polymer flowing through said apertures form into hollowfilaments; and a shim secured between said distributor and saidspinneret, said shim having a plurality of openings, each of saidopenings having adjacent first and second portions, wherein said firstportion forms a continuous path from said outer flow passage, throughsaid openings to said holes, and said second portion forms a continuouspath from said inner flow passage, through said openings to said holes.3. The spin pack assembly of claim 2 wherein said apertures havedifferent cross-sectional areas.
 4. The spin pack assembly of claim 3wherein said plurality of apertures consists of a first aperture and asecond aperture.
 5. The spin pack assembly of claim 4 wherein said firstand second apertures are generally C-shaped.
 6. The spin pack assemblyof claim 2 wherein said outer flow passages have a bottom section thatis axially offset from said holes such that if said bottom sections wereextended said bottom sections would be positioned within a first part ofsaid hole.
 7. The spin pack assembly of claim 6 wherein said first partis a part of the hole closest to a center of said spinneret.
 8. The spinpack assembly of claim 6 wherein said second portion extends from saidfirst portion in a direction away from said first part of said hole toform a continuous course from said spinneret, through said secondportion, to a remaining part of said hole opposed to said first part. 9.The spin pack assembly of claim 8 wherein said first portion is circularshaped and coaxial with said holes and said second portion is block-arcshaped.
 10. The spin pack assembly of claim 9 wherein said secondportion spans in an arc in a range from about 90 to about 120 degrees.11. The spin pack assembly of claim 10 wherein said second portion spansin an arc approximately 120 degrees.
 12. The spin pack assembly of claim8 wherein said apertures have different cross-sectional areas.
 13. Thespin pack assembly of claim 12 wherein said plurality of apertures is afirst aperture positioned in said first part and a second aperturepositioned in said remaining part, said first aperture having a largercross-sectional area than said second aperture and said first and secondapertures are generally C-shaped, and said holes are axially offset fromrespective said bottom sections so that said bottom sections would bepositioned within said first part if extended.
 14. The spin packassembly of claim 13 wherein said first part is closer to a center ofsaid spinneret than said remaining part.